CN1048650C - Preparation process of catalyst for waste gas purification - Google Patents
Preparation process of catalyst for waste gas purification Download PDFInfo
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- CN1048650C CN1048650C CN96102488A CN96102488A CN1048650C CN 1048650 C CN1048650 C CN 1048650C CN 96102488 A CN96102488 A CN 96102488A CN 96102488 A CN96102488 A CN 96102488A CN 1048650 C CN1048650 C CN 1048650C
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Abstract
The present invention relates to a method for preparing a catalyst for purifying exhaust gas, which has the technical scheme that part of the pre-determined amount of thin diaspore is made into slurry which is acidified by hydrochloric acid; the rest thin diaspore and aluminium sol are added; a water solution of 2.5 to 15.0% of ferro chromo lignosulfonate (dry basis alumina weight as the basis of calculation) is added after the slurry is aged; the obtained slurry is coated on the surface of a cellular cordierite carrier; loading noble metal, rare earth metal and transition metal are made into the catalytic agent through drying and calcination. The catalytic agent has the advantages of large specific surface area and superior heat stability and can be used for purifying processes of harmful gas including automobile exhaust gas containing carbon monoxide (CO), hydrocarbon (HC), oxynitride (NOX), etc.
Description
The invention relates to a kind of Preparation of catalysts method that is used for waste gas purification, specifically, be about a kind of be used to comprise vehicle exhaust contain carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxidized compound (NO
x) wait the preparation method of the cleaning catalyst of pernicious gas.
Common purification process normally makes vehicle exhaust pass through a beds, makes harmful constituent such as CO, HC and NO in the tail gas
xDeng being transformed into CO harmless or that harm is little
2, H
2O, N
2Deng composition.For adapting to the working order of automobile engine under different temperatures.Catalyst carrier adopts high temperature resistant, heat shock resistance, corrosion resistant ceramic honeycomb body.Ceramic honeycomb body commonly used mostly is cordierite greatly and makes, and the cordierite specific area is minimum, is unfavorable for the load and the dispersion of metal active constituent.Therefore, the aluminium oxide that people will have bigger serface is applied to the ceramic honeycomb surface, makes catalyst at the area load metal active constituent of aluminium oxide again.Introduced a kind of exhaust gas purifying catalyst as CN1055302A, be that the noble metal active component is weighed the scale deposits of % on aluminium oxide or zirconia with 5-30, and then with this aluminium oxide that contains noble metal or zirconia with do not contain noble metal aluminium oxide and cerium oxide and mix, grind into moisture thin pulp with ball mill and be coated on cellular porcelain body surface, after the drying, 100-600 ℃ of roasting makes catalyst.The used aluminium oxide of this patent is an activated alumina, and its surface area is a 5-200 rice
2/ gram.
As everyone knows, along with the rising of temperature, aluminium oxide can produce following phase transformation:
With the change of crystalline phase, the specific area of aluminium oxide also reduces thereupon, thereby causes the catalyst activity component, and particularly the noble metal active component is built up and is wrapped, catalyst activity reduction consequently, the lost of life.
Therefore, people attempt aluminium oxide is carried out modification, make it at high temperature still have bigger specific area, then with this modification aluminium oxide do the catalyst carrier coating material, make cleaning catalyst adapt to the working order of automobile engine under high and low temperature, keep catalyst activity.For example United States Patent (USP) 5,260, use phosphate in 241, as ammonium phosphate aluminium oxide carried out modification and handle, and obtained to have than bigger serface AlPO
4Content is phosphate-Al of 3～12 heavy %
2O
3,, contain the AlPO of 10 heavy % as an example
4Aluminium oxide still has 162 meters after 850 ℃ of roastings
2The specific area of/gram.This patent makes exhaust gas purifying catalyst with the surperficial back loading reactive metal that predecessor's slurries of this modified aluminas directly are coated on cellular porcelain body, has obtained result preferably.But the phosphorus that uses in this patent easily makes the noble metal in the catalyst poison, and it sees consent road, particularly aperture, causes average pore size to change, and the diffusion of restricted activity component finally causes catalyst activity obviously to descend.
In addition, CN1097351A also discloses a kind of preparation microspheroidal γ-Al
2O
3Method, this method is to add surplus boehmite and aluminium colloidal sol again after the part boehmite acidifying in the scheduled volume, to make microspheroidal γ-Al through steps such as spray shaping, roastings
2O
3, aluminium oxide obtained by this method has characteristics such as intensity height, specific surface be big.
The objective of the invention is on the basis of above-mentioned prior art, to provide a kind of preparation method of exhaust gas purifying catalyst, make this catalyst have activity and heat endurance preferably.
Preparation of catalysts method provided by the invention is: the aluminium oxide slurries of preparation ferrochrome lignosulfonate (being called for short FCLS) modification, again these slurries are coated on the cordierite honeycomb carrier surface, make the complex carrier with aluminum oxide coating layer, carried noble metal, rare earth metal and transition metal active component make catalyst then.
Wherein the preparation method of said complex carrier is as follows:
(1) boehmite and the decationized Y sieve water of the heavy % of 25-75 in the scheduled volume are made the slurries that solid content is 10～15 heavy %, it is 1.5～4.0 that adding hydrochloric acid is transferred its pH value, and the boehmite that adds surplus again is stirred to slurries and is equal colloid shape.The boehmite weight ratio that the front and back secondary adds is preferably 1: 1.
(2) add Al
2O
3Content is that the heavy % of 21.5-23.5, Al/Cl weight ratio are that 1.15～1.25 aluminium colloidal sol continues to stir 30～60 minutes.
(3) 50～70 ℃ were worn out 1～3 hour.
(4) aqueous solution that adds the ferrochrome lignosulfonate account for butt alumina weight 2.5～15.0% stirs.
(5) the cordierite honeycomb carrier is immersed above-mentioned slurries, takes out the back and blows away unnecessary slurries in the duct with compressed air, in room temperature to 120 ℃, preferably 40-60 ℃ dry 2-4 hour, 500-600 ℃ roasting 2-4 hour.
In above-mentioned preparation process, used boehmite Al
2O
3Content is the heavy % of 20-60, and the weight ratio of boehmite and aluminium colloidal sol is (with Al
2O
3The calcination base is for calculating benchmark) be 90-95: 5～10.
Reactive metal (is to calculate benchmark with the catalyst weight) composed as follows in the catalyst that the method for the invention provides is made:
(1) at least a noble metal that is selected from Rh or Pt, Pd.When noble metal was selected from Rh, its content was 0.03～0.5% when noble metal is selected from Pt or Pd, and its content is 0.1～2.0%; When noble metal was selected from Rh and Pt, the Pt/Rh weight ratio was 3～10: 1, preferably 3～5: 1.
(2) be selected from the rare earth metal of any one or a few mixing among La, Ce, the Pr, its content is 1.2～12.0%.
(3) be selected from the transition metal of any one or a few mixing among Cr, Fe, Mn, Co, Ni, the Cu, its content is 1.2～8.5%.
This catalyst prepares with step impregnation method: get the cordierite carrier that scribbles aluminum oxide coating layer in right amount, with the cerium of scheduled volume or nitrate or the hydrochloride or the rich cerium rare earth chloride solution dipping of lanthanum, soaking the back carrier purges with compressed air, remove the unnecessary liquid in the honeycomb support duct, 110-120 ℃ of drying 2～4 hours, 500～600 ℃ of roastings 2～4 hours, carry out double-steeping with containing Pt or Pd solution or transition metal salt solution then, solution with rhodium-containing carries out dipping three times again, the drying when each dipping back carrier all floods by the first time, calcination steps is handled.At last, be warming up to 500 ℃ with reducibility gas continuously from room temperature and handle, heating rate is 11 ℃/minute, is cooled to room temperature then.Reprocessing once so again.Described reducibility gas comprises the synthesis gas that hydrogen, carbon monoxide, hydrocarbon or above-mentioned three kinds of gases of sneaking into arbitrary proportion and carbon dioxide are formed in nitrogen.
The present invention is owing to added modifier ferrochrome lignosulfonate (FCLS) in the aluminum oxide coating layer slurries, this modifier can suppress the phase transformation of aluminium oxide when high temperature, and can adjust slurry viscosity, make it have stronger tack, make slurries can be coated on the surface of honeycomb support more equably, the prepared aluminium oxide of the present invention at high temperature still has bigger specific area, as after 850 ℃ of roastings, still has 200 meters
2The surface area of/gram, therefore make the catalyst activity component particularly noble metal can be evenly distributed on the carrier, thereby activity of such catalysts and stability are strengthened.
Fig. 1 is for adding aluminium oxide behind the FCLS at 6 hours X diffraction crystalline phase figure of 900 ℃ of roastings.
Fig. 2 is not for to add the aluminium oxide of modifier FCLS at 6 hours X diffraction crystalline phase figure of 900 ℃ of roastings.
Fig. 3 is the differential thermal analysis curve of the aluminium oxide behind the adding FCLS.
Fig. 4 is the differential thermal analysis curve that does not add the aluminium oxide of modifier FCLS.
Fig. 5 is for adding aluminium oxide and the specific area variation diagram of commercial alumina under high-temperature roasting of FCLS.
Further specify the present invention below by example.
Example 1
The preparation method of this case introduction aluminum oxide coating layer of the present invention.
Get 250 gram boehmite (Al
2O
3Content is 22%, the Zhou village catalyst plant is produced), adding 360 gram decationized Y sieve water stirred 30 minutes, the control slurry solid content is 10-15%, adds 1: 1 hydrochloric acid (chemical pure, the Beijing Chemical Plant produces) 19 milliliters, adjusting the slurries pH value is 3.45, add 250 gram boehmites again and stirred 30 minutes, the aqueous solution that makes slurry contain 10 heavy %FCLS (technical pure, red flag chemical plant, tree peony city produces) stirs.Make to apply and use moisture thin pulp.
(dahua ceramics factory in Beijing produces with commercially available cordierite honeycomb carrier, φ is 16.7 millimeters a sheet, immerse the moisture thin pulp of above-mentioned coating, take out then, blow away unnecessary slurries in the duct with compressed air, 110 ℃ of dryings 2 hours, 550 ℃ of roastings made complex carrier AL-A in 2 hours, and wherein the content of aluminium oxide is every liter of carrier 52 grams.Surveying specific area with low-temperature nitrogen adsorption method is 252 meters
2/ gram.
Prepare complex carrier AL-B as stated above, different is that baking temperature is 50 ℃, and be 24 hours drying time, and specific area is 288 meters
2/ gram.
Example 2
The modifier FCLS that this example explanation the inventive method adds has the effect that suppresses the aluminium oxide phase transformation.
The coating of getting in the example 1 preparation is with moisture thin pulp and use and prepare with quadrat method but do not add the slurries of modifier FCLS, 110 ℃ of dryings 2 hours, and 550 ℃ of roastings made γ-Al in 2 hours
2O
3Powder A and B (B is the contrast sample).
With two kinds of γ-Al of A, B
2O
3Powder is its X-ray diffraction crystalline phase figure (as shown in Figure 1 and Figure 2) then 900 ℃ of roastings 6 hours, and used determining instrument is Japanese DfMAX-IIIA type X-ray diffractometer of science.Comparison diagram 1, Fig. 2 as can be known, aluminium oxide does not have tangible phase transformation peak among Fig. 1, illustrate add modifier FCLS after, the phase transformation of aluminium oxide has obtained inhibition.
Example 3
The made aluminium oxide of this example explanation the present invention has heat endurance preferably.
γ-Al that example 2 is made
2O
3Powders A, B, with USA DupoutInstrument 990 type thermal analyzers, heating rate with 10 ℃/minute is done differential thermal analysis, the result as shown in Figure 3, Figure 4, as seen from the figure, the alumina powder A that adds FCIS the peak do not occur destroying yet in the time of 1100 ℃, and the alumina powder B that does not add FCLS the peak promptly occurs destroying at 966 ℃.It is thermally-stabilised preferably to illustrate that the made aluminium oxide of the present invention has.
Example 4
The made aluminium oxide of this example explanation the present invention has bigger specific area.
Example 2 made alumina powder A and commercial alumina powder C are surveyed its BET specific area after roasting under the different temperatures, the result as shown in Figure 5.As seen from the figure, the made aluminium oxide of the present invention still has bigger specific area under high-temperature roasting, and as 850 ℃ of roastings, specific area is 200 meters
2/ gram, even roasting under 950 ℃ high temperature, specific area is high than commercial alumina still, its value reaches 150 meters
2/ gram.
Example 5-9
Following case introduction Preparation of catalysts.
Get the carrier A L-A that a certain amount of example 1 makes, lanthanum chloride (chemical pure with 40 milliliters, the Beijing Chemical Plant produces) solution or cerous chlorate (chemical pure, the Beijing Chemical Plant produces) solution impregnation, purge with compressed air then, remove the unnecessary liquid in the honeycomb support duct and survey its volume, 110～120 ℃ of dryings 2 hours, 550 ℃ of roastings 2 hours.And then with 40 milliliters of chloroplatinic acid (chemical pures, the Chang Ling catalyst plant) or chromium chloride (chemical pure, Beijing Chemical Plant's production) carry out double-steeping, use 40 milliliters of radium chloride (chemical pures again, the Beijing Chemical Plant produces) or palladium bichloride (chemical pure, the Beijing Chemical Plant produces) carry out dipping three times, each dipping back carrier all drying, the calcination steps when flooding is for the first time handled, at last, the synthesis gas with similar vehicle exhaust (wherein contains H
22500ppm, HC600ppm, CO10000ppm, all the other are N
2) be warming up to 500 ℃ with 11 ℃/minute heating rates continuously from room temperature, and then be cooled to room temperature.Reprocessing once promptly gets catalyst A～E so again.
In each example in carrier A L-A consumption and the maceration extract active metallic content list in the table 1, wherein catalyst D, E have only flooded a kind of noble metal active component, each catalyst activity metal group becomes to see Table 2, its value is calculated by following formula
Comparative Examples 1
Method with example 5～9 prepares comparative catalyst N, and the maceration extract of use and active metallic content be all with catalyst C, and the preparing carriers method is with example 1, does not add modifier FCLS in the used aluminum oxide coating layer slurries when different is the preparation carrier.
Comparative Examples 2
Prepare comparative catalyst M with commercial alumina.
With 100 gram aluminium oxide (the made microballoon γ-Al in Beijing Chemical Research Institute
2O
3) place ball mill to add decationized Y sieve water (solid content is 50%), wet-milling is after 4 hours, makes to apply to use moisture thin pulp, makes carrier by the painting method of example 1, and then prepares catalyst by the method for example 5～9, and reactive metal is formed with catalyst C.
Example 10
The catalyst that this example explanation the inventive method provides has the good low-temperature purifying property.
Adopt following method to estimate: catalyst is pulverized, getting 5 milliliters of 5～20 order particles internal diameter of packing into is that reactor is inserted in the heating furnace, is warming up to 550 ℃ with 11 ℃/minute speed in 14 millimeters the quartz reactor, form the preparation synthesis gas by air distributing device simulated automotive tail gas, this synthesis gas is with N
2Be the basis, wherein contain CO9000ppm, H
22000ppm, HC240ppm, CO
210800ppm, NO
x700ppm, O
220000ppm, this synthesis gas was with 24000 hours
-1Volume space velocity by quartz reactor, 20 ℃ of every intensifications, assaying reaction device exit generates CO, HC and the NO in the gas
xConcentration, calculate the cleaning harmful gas rate according to following formula then.
With purifying rate reaction temperature is mapped, try to achieve purifying rate and be 50% o'clock reaction temperature T
50, this value can be used as the standard of evaluation catalyst low temperature purification performance, now the low temperature purification performance of catalyst of the present invention and contrast medium is listed in the table 3, and the result shows that catalyst C of the present invention has lower T
50Temperature, and NO
xThe highest purifying rate value maximum.
The generation gas of simulation synthesis gas and reactor exit is made up of following Instrument measuring: carbon monoxide (CO): QGS-08 type CO analyzer, Beijing Analytical Instrument Factory; Carbon dioxide (CO
2): QGS-08 type CO
2Analyzer, Beijing Analytical Instrument Factory; Oxygen (O
2): GXH-500 type oxygen analyzer, Beijing Analytical Instrument Factory; Hydrocarbon (HC): 31100RES type hydrocarbon analyzer, Japan produces; Nitrogen oxide (NO
x): Model-10 type chemiluminescence NO
xAnalyzer, U.S. Thermo Electron Corp..
Example 11
The catalyst that this example explanation the inventive method provides has stability preferably.
With catalyst C of the present invention and comparative catalyst N roasting 6 hours under 600～900 ℃ high temperature, estimate by the method for example 10 then, try to achieve the T of CO, HC
50Value and NO
xMaximum conversion the results are shown in table 4.As shown in Table 4, after comparatively harsh high-temperature process, catalyst C of the present invention compares with comparative catalyst N, still has lower CO, the T of HC
50Value, particularly after 900 ℃ high-temperature roasting, catalyst of the present invention is to the T of CO
50Be worth still lowlyer, show that catalyst of the present invention has preferably stability.
Example 12
The activity of such catalysts and the selectivity of this case introduction load different metal active component.
With catalysis Ji A, B of the present invention, D, E, estimate with the method for example 10, the results are shown in Table 5.As shown in Table 5, the T of platinum catalyst CO
50Be worth lowlyer, carried palladium catalyst is to NO
xRemoval efficiency higher, but take all factors into consideration, the clean-up effect of catalyst B is better.
Table 1
| | 1 | 2 | 3 | 4 | 5 | |
| The catalyst numbering | A | B | C | D | E | |
| The carrier amount, gram | 11.56 | 11.61 | 8.57 | 8.52 | 8.90 | |
| Flood for the first time | Maceration extract | Lanthanum chloride | Cerous chlorate | Cerous chlorate | Chloroplatinic acid | Palladium bichloride |
| Tenor, grams per milliliter | 0.165 | 0.33 | 0.33 | 0.04 | 0.019 | |
| Difference *, milliliter | 3.5 | 3.5 | 3.0 | 3.0 | 3.0 | |
| Flood for the second time | Maceration extract | Chromium chloride | Chloroplatinic acid | Chloroplatinic acid | - | - |
| Tenor, grams per milliliter | 0.19 | 0.04 | 0.01 | - | - | |
| Difference *, milliliter | 3.5 | 3.5 | 3.0 | - | - | |
| Flood for the third time | Maceration extract | Palladium bichloride | Radium chloride | Radium chloride | - | - |
| Tenor, grams per milliliter | 0.019 | 0.0113 | 0.00283 | - | - | |
| Difference *, milliliter | 3.5 | 3.5 | 3.0 | - | ||
*This value is the volume difference of maceration extract before and after the dipping.
Table 2
| The catalyst numbering | Metal is formed, heavy % |
| A | La 4.4 Cr 5.2 Pd 0.51 |
| B | Ce 8.9 Pt 1.08 Rh 0.31 |
| C | Ce 10.3 Pt 0.31 Rh 0.09 |
| D | Pt 1.4 |
| E | Pd 0.6 |
Table 3
| The catalyst numbering | T 50，℃ | NO xMaximum conversion, % | |
| CO | HC | ||
| C | 210 | 343 | 17.0 |
| N | 265 | 360 | 10.0 |
| M | 242 | 445 | 8.5 |
Table 4
| Sintering temperature, ℃ | The catalyst numbering | T 50，℃ | NO xMaximum conversion, % | |
| CO | HC | |||
| 600 | C | 210 | 343 | 17 |
| N | 265 | 362 | 10 | |
| 800 | C | 230 | 370 | 25 |
| N | 240 | 378 | 27 | |
| 900 | C | 252 | 550 | 34 |
| N | 290 | 580 | 32 | |
Table 5
| The catalyst numbering | Metal component | T 50，℃ | NO xMaximum conversion, % | |
| CO | HC | |||
| A | Pd-Cr-La | 211 | 289 | 9.0 |
| B | Ph-Pt-Ce | 199 | 284 | 32.9 |
| D | Pt | 146 | 365 | 24.6 |
| E | Pd | 235 | 395 | 42.3 |
Claims (10)
1, a kind of preparation method of exhaust gas purifying catalyst, be to do complex carrier with the cellular porcelain body of the en-block construction that scribbles aluminum oxide coating layer, carried noble metal, rare earth metal and transition metal active component make catalyst, it is characterized in that complex carrier is made by the following step:
(1) boehmite and the decationized Y sieve water of the heavy % of 25-75 in the scheduled volume are made the slurries that solid content is 10～15 heavy %, it is 1.5～4.0 that adding hydrochloric acid is transferred its pH value, and the boehmite that adds surplus again is stirred to slurries and is equal colloid shape;
(2) adding aluminium colloidal sol continues to stir 30～60 minutes;
(3) 50～70 ℃ were worn out 1～3 hour;
(4) aqueous solution that adds the ferrochrome lignosulfonate account for butt alumina weight 2.5～15.0% stirs;
(5) the cordierite honeycomb carrier is immersed above-mentioned slurries, take out the back and blow away unnecessary slurries in the duct, dry, roasting with compressed air.
2, in accordance with the method for claim 1, it is characterized in that the weight ratio of boehmite and aluminium colloidal sol in the slurries is (with Al
2O
3The calcination base is for calculating benchmark) be 90-95: 5-10.
3, in accordance with the method for claim 1, the content that it is characterized in that complex carrier floating coat aluminium oxide is every liter of carrier 40-60 gram.
4, in accordance with the method for claim 1, the weight ratio that it is characterized in that the boehmite of twice adding described in (1) is 1: 1.
5, in accordance with the method for claim 1, it is characterized in that containing Al in the described boehmite
2O
3The heavy % of 20-60 contains Al in the aluminium colloidal sol
2O
321.5-23.5 heavy %, the Al/Cl weight ratio of aluminium colloidal sol is 1.15-1.25.
6, in accordance with the method for claim 1, it is characterized in that the baking temperature described in (5) is a room temperature to 120 ℃, sintering temperature is 500-600 ℃.
7, in accordance with the method for claim 1, it is characterized in that step impregnation method is adopted in the load of metal active constituent, after every dipping one component, need drying, roasting to soak another component again, each reactive metal (is benchmark with the catalyst weight) composed as follows:
(1) at least a noble metal that is selected from Rh and/or Pt, Pd, when noble metal was selected from Rh, its content was 0.03-0.5%, its content is 0.1-2.0% when being selected from Pt or Pd;
(2) rare earth metal that is selected from any one or a few mixing among La, Ce, the Pr of 1.2-12.0%;
(3) transition metal that is selected from any one or a few mixing among Cr, Fe, Mn, Co, Ni, the Cu of 1.2-8.5%.
Its content is 0.1-0.9% when 8, in accordance with the method for claim 7, it is characterized in that the noble metal described in (1) is selected from Pt or Pd.
9, in accordance with the method for claim 7, when it is characterized in that the noble metal described in (1) is selected from Rh and Pt, the Pt/Rh weight ratio is 3-10: 1.
10, in accordance with the method for claim 7, when it is characterized in that the noble metal described in (1) is selected from Rh and Pt, the Pt/Rh weight ratio is 3-5: 1.
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|---|---|---|---|
| CN96102488A CN1048650C (en) | 1996-03-21 | 1996-03-21 | Preparation process of catalyst for waste gas purification |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96102488A CN1048650C (en) | 1996-03-21 | 1996-03-21 | Preparation process of catalyst for waste gas purification |
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| CN1048650C true CN1048650C (en) | 2000-01-26 |
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| CN96102488A Expired - Fee Related CN1048650C (en) | 1996-03-21 | 1996-03-21 | Preparation process of catalyst for waste gas purification |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1872409B (en) * | 2005-05-31 | 2010-12-01 | 中国石油化工股份有限公司 | Cleaning catalyst for tail gas of automobile, and preparation method |
| CN100371072C (en) * | 2005-09-30 | 2008-02-27 | 清华大学 | Preparation process of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide |
| CN101589005A (en) * | 2006-06-30 | 2009-11-25 | 康宁股份有限公司 | High porosity filters for 4-way exhaust gas treatment |
| CN102580733A (en) * | 2011-12-15 | 2012-07-18 | 无锡威孚环保催化剂有限公司 | Method for preparing Pd-only catalyst used for tail gas purification of universal minitype petrol engines |
| CN102888242B (en) * | 2012-10-20 | 2014-06-18 | 东北石油大学 | Method for decreasing FCC regenerative process NOx by DeNOx additive |
| CN105396543B (en) * | 2015-12-17 | 2018-02-16 | 广州南枢电子科技有限公司 | A kind of fuel oil catalyst |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1042092A (en) * | 1988-10-26 | 1990-05-16 | 中国科学院生态环境研究中心 | A kind of complex rare-earth oxidate containing valuable metal type honeycomb catalyst and preparation method thereof |
-
1996
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1042092A (en) * | 1988-10-26 | 1990-05-16 | 中国科学院生态环境研究中心 | A kind of complex rare-earth oxidate containing valuable metal type honeycomb catalyst and preparation method thereof |
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